The present invention relates generally to the field of sealing devices, and more particularly to a sealing device adapted for use specifically with a particularly type of motorcycle toe shift mechanism.
It is virtually common knowledge today, especially among those who are at all knowledgeable about motorcycles, that they are driven by an internal combustion engine that operates basically on the same principles as those applicable to automobile engines, and that several of the major driving components found in the drive train of automobiles are also found in motorcycles. One of these components is the transmission, the function of which, as is also well known, is to provide a range of torque to speed ratios that permits the engine of the motorcycle (or for that matter any other type of internal combustion engine vehicle, although this discussion is confined to the motorcycle) to drive the motorcycle at varying speeds for a given amount of engine torque. Thus, the transmission provides a variety of gear ratios through which the engine transmits power to the driving wheel of the motorcycle so that the power transmitted to the driving wheel is greatest when the motorcycle first begins to move to achieve maximum acceleration, and is least when the motorcycle is traveling at a relatively high rate of speed in order to maintain that speed or accelerate slowly at the same range of engine RPMs as that which provided the high engine power for maximum acceleration.
For several decades there has been a gradual shift in the manner of operation of automobile transmissions from fully manual to fully automatic, so that the vehicle driver neither has to operate a clutch mechanism or a transmission shift lever. This shift, however, has not occurred with respect to motorcycles for a number of reasons; one is the high level of complexity of automatic transmissions and the consequent additional cost that would be entailed in providing motorcycles with this feature. Another is the added weight of the transmission that would necessitate a more powerful engine for a given size motorcycle than is otherwise necessary. Still another reason, and a significant one, is that a large segment of those who ride motorcycles prefer a manual transmission since the manual shifting of gears and operation of a clutch mechanism contribute significantly to the shear pleasure of operating a motorcycle.
For whatever the reason, motorcycle manufacturers have steadfastly retained manual shifting of gears in motorcycles. The only significant improvement that has been made is that the manually operated gear shift lever that was formerly mounted on a frame adjacent the gas tank and moved in a forward and backward direction to select gears, in a manner similar to the movement of a floor mounted shift lever in an automobile having an automatic transmission, has been replaced with a toe shift mechanism by which the gear are shifted. Thus, in virtually all motorcycles manufactured today, there is a hand grip and cable mechanism by which the operator engages and disengages the clutch mechanism to permit the transmission gears to shift, and there is a toe shift mechanism by which the operator actually shifts the gears. The toe shift mechanism includes a first lever which is connected to one end of a shaft that is rotatably mounted in a housing, with an annular spacer around the shaft between the outer end of the housing and the lever to prevent the shaft from shifting longitudinally within the housing. A second lever is connected to the other end of the shaft, and is also connected to a rod that extends into the transmission assembly which in turn is connected to a ratchet mechanism that actually shifts the gears. When the operator momentarily depresses the first lever, it oscillates the shaft within the housing, which in turn rocks the second lever back and forth to cause the rod to reciprocate, thereby actuating the ratchet mechanism in the transmission to shift the gears. The construction of the ratchet mechanism is such that the gears are shifted in sequence, that is, from first to second, to third, to fourth and then to fifth, with the reverse sequence being followed when shifting down from the highest speed gear to the lowest. It is thus apparent that during routine operation of a motorcycle, especially within urban areas having heavy traffic and frequent traffic signals and/or stop signs, or other areas of frequent acceleration and deceleration, the aforementioned shaft is constantly being oscillated within the housing.
It is therefore necessary to maintain the shaft and shaft housing constantly lubricated to prevent excessive wear on the adjacent surfaces of these parts. Without such lubrication, these adjacent surfaces would wear excessively and unevenly over a period of time, with the result that the shaft would not fit properly in the housing and would begin to wobble during activation of the toe shift mechanism This in turn would cause additional wear on various portions of the shaft and the housing to the point where the toe shift mechanism would cause erratic shifting of the transmission gears. The lubrication is accomplished in much the same manner as greasing wheel bearing on an automobile, that is, by injecting grease into the housing through a suitable grease fitting mounted on the housing.
The problem that occurs is that the nature of the toe shift mechanism is such that grease can seep or ooze between the inner wall of the housing and the outer wall of a shaft, since there are no grease seals within the housing to prevent the grease from oozing out. The result is that over a period of time, grease gradually coats the protruding portion of the shaft, the surrounding housing, the annular spacer between the adjacent end faces of the housing and the annular spacer, and even portions of the lever that connects the shaft with the foot pedal by which the shaft is rotated. Typically, some of these parts are chrome plated for decorative purposes, and the presence of grease renders them unsightly. It should be understood that typically the owners of motorcycles of the type under consideration, which are typically relatively expensive, high end prestigious models of motorcycles, such as those manufactured by Harley-Davidson, are very sensitive about the appearance of their vehicles, and they meticulously maintain them, constantly cleaning them to avoid the buildup of grease on and around the toe shift mechanism. This, of course, requires some degree of effort, is time consuming and considerably annoying to the great bulk of owners of this type of motorcycle.
While it might appear obvious simply to provide suitable sealing elements, such as O-rings, within the housing to prevent grease from escaping, the problem is that the manufacturer of these motorcycles has been using the same parts for the toe shift mechanism for so long, and it has been so successful, that it is unlikely that the manufacturer will expend either the effort or the money to redesign the shaft housing and the shaft to accommodate any form of sealing elements. In the approximately 15 years that this toe shift mechanism has been on the market, approximately 150,000 units have been sold, and redesigning these parts simply to avoid a vexing problem to the operators would not be cost effective for the manufacturer.
Thus, there is a need for a sealing device for motorcycles having this type of toe shift mechanism which replaces the existing annular spacer so as to maintain the same spacing between the inner face of the toe shifting lever and the outer face of the grease housing that presently exists yet prevents the escape of grease between the adjacent ends of the grease housing and spacer.